Ticked Off: Understanding the Asian Longhorned Tick with Dr. Hayley Springer

Join Berks County dairy educator, Kasey Hower, as she interviews Dr. Hayley Springer, the Animal Health Division Chief for the Bureau of Animal Health and Diagnostics Service at the Pennsylvania Department of Agriculture. They discuss the emerging threat of the Asian Longhorned Tick and what dairy producers can do to manage this pest. 

Transcript

Welcome And Guest Introduction

Speaker 1 0:10

Welcome to Bovine Banter with the Penn State Extension Dairy Team. I'm Kasey Hower and I'm a dairy educator based in Berks County, Pennsylvania. Joining us today is Dr. Hayley Springer, the Animal Health Division Chief for the Bureau of Animal Health and Animal Diagnostic Service at the Pennsylvania Department of Agriculture. And this season we've been focusing mostly on organic dairy production, but today we're going to be talking about the emerging threat of the Asian longhorned tick and grazing management, which can be relevant to both our organic and conventional producers. But I just wanted to start by thanking Dr. Springer for being with us today. And to get us started, can you please tell us a little more about yourself and your current role with the Pennsylvania Department of Ag?

Speaker 0:54

Sure.

Dr. Springer’s Role In PA

Speaker 0:55

Thank you so much for the invite today. I'm really looking forward to being here. So as the Animal and Poultry Health Division Chief for the Bureau of Animal Health and Diagnostic Services, I see oversee a lot of the disease prevention programs here in Pennsylvania, but I also have the opportunity to be involved in other areas, including forays into testing for Thierelia Orientalis, which is a disease closely related to the Asian Longhorn Tick. So I have gotten to be involved in a lot of the state level management of this tick and this disease and seeing how our different areas of the state can interact to better manage the challenges that we're going to see with the Asian Longhorn tick.

Speaker 1 1:38

Okay, great.

Why This Tick Is Different

Speaker 1 1:39

And so to tell us a little bit more about this tick, which is an emerging threat to cattle, what makes it different from what producers might be used to seeing?

Speaker 1:50

So I think the biggest thing that really makes it different is that it's new. This is not an endemic tick. So this is a tick that was introduced to the United States. It was first recognized here in the United States in 2017, but historical records and looking back at old tick collections have shown that it's been here at least since 2010. So in terms of ticks in general, that's still a very, very new tick. And so being something new, we're still seeing how it's going to impact the overall biology and where it's going to end up spreading to. In terms of the tick itself, when we look at how it impacts cattle, there's two really big factors. This is really the first tick we have in the northeastern US that's vectoring a significant disease of cattle. And we'll certainly talk more about Thylera orientalis genotype Ikeda, which is that disease. The other really big challenge of this tick is that it can cause population explosions that can then actually cause a swarming level of infestation in cattle that can directly impact their health.

Speaker 1 3:01

Okay. So you've talked a little bit about the specific disease that this tick causes. Can you elaborate on that a little bit more and talk about our current understanding and emerging concerns with that?

Theileria Disease And Why It’s Serious

Speaker 3:13

Sure. So the primary disease that we're concerned with in terms of the Asian longhorn tick in cattle is Thierelia orientalis genotype Ikeda, which is a bloodborne pathogen that impacts the red blood cells. It is transmitted by this tick from cattle to cattle. And one of the big challenges of this disease is that it can cause very severe disease in cattle. It causes ultimately anemia, and these cattle can be really weak. And I think the biggest challenge we face with this disease is we don't have a treatment, and it isn't a disease that the cattle can completely clear from their system. So once an animal gets this disease, they're actually positive for life.

Speaker 1 3:58

Okay.

Anemia Signs Producers Can Spot

Speaker 1 3:59

So what are some of the clinical signs? I know you said anemia is the main thing that you might see, but what are some more clinical signs that our producers might be noticing?

Speaker 4:08

Sure. It's good to watch for these clinical signs because the reality is whether we're dealing with thierelia orientalis genotype Ikeda or whether we're dealing with a severe tick infestation, the ultimate result is going to be anemia either way. And so some of the things we might see in anemic cattle are things like lethargy, weakness, exercise intolerance. They might show what we call icterus, which is a yellowing of mucous membranes, or you might see it in the whites of their eyes. We can also see hematuria, particularly in the thierelia orientalis, and what that means is blood in the urine. So rather than looking that normal yellow color, the urine might be more of a red to brown color. And when this gets severe, we can actually see acute death. So we may just see animals that we find dead and may not have a good explanation for. So there's a pretty wide range of clinical signs that we can see, but a lot of it circles around that weakness and lethargy that we see with anemia.

Speaker 1 5:10

Do we know how long from like initial exposure to when that animal might be presenting clinical signs?

Speaker 5:17

I think one of the challenges we face there is that we often don't know when the initial bite was. And so I think from a clinical perspective and an on-farm perspective, I don't know that we've got a great idea of that. So I don't have a good solid answer for you on that one.

Speaker 1 5:37

Okay.

Parthenogenesis And Tick Population Surges

Speaker 1 5:38

So you mentioned that this tick has a unique biology. Can you talk about that a little bit more with how it reproduces?

Speaker 5:45

Sure. So this tick, as I mentioned earlier, can result in really, really big population explosions. And this can cause infestations that are so bad that can actually cause anemia in the animals being bitten by these ticks because there are just so many of them. And the biology behind that population explosion is that these ticks are what we call parthenogenic. And what that means is they do not need a male to reproduce. A single female can lay two to three thousand eggs. So even transporting a single animal can start a whole new population because we don't need to have a male tick involved. And in fact, the vast majority of Asian longhorn ticks that have been found in the United States are female. We really don't have significant populations of males. In fact, it took until over five years after it was first identified in the US to find the first male Asian longhorn tick in the US. So it is a really unique biology in that a transport of a single tick can start a whole new population. And then because 100% of the ticks, or nearly 100% of the ticks, are female, they can all lay eggs. And so the generation explosion is much higher because 100% of the offspring are then able to lay eggs and make more ticks.

Milk And Reproduction Risks

Speaker 1 7:02

Gotcha. So how does tick burden translate into milk production or reproductive performance losses for dairy cattle?

Speaker 7:11

So we don't have a lot of real solid data on this. There are some reports out of New Zealand that estimate as much as a 25% reduction in milk production in heavy infestations of Asian longhorn ticks. And New Zealand and Australia are areas where this tick is also an invasive species, much like it is here in the US. And so that it that's one thing we have on the milk production side is that it could be as much as 25% in severe infestations. In terms of reproductive impact, we really don't have solid numbers on this, but certainly if we have severe infestations heavy enough to cause a chronic anemia in breeding cattle, that's going to cause stress, and any stress is going to impact reproduction. So we certainly could have reproductive impacts just from that chronic stress associated with anemia. But then we also can bring in thierelia orientalis into this. That disease itself can, when severe enough, can cause abortion as well. So we really have two areas where it could impact reproductive performance.

Speaker 1 8:17

Okay, so if a cow is exposed to this tick, is she guaranteed to get thierelia orientalis? Or not?

Speaker 8:26

So is it there's not a guarantee. It's much like other tick-vectored species. If you think about Lyme disease, not every tick carries Lyme disease, but they certainly can, um, even if we're looking at the right species of ticks. So it's not a guarantee, but if we have positive animals and we have ticks, we can assume there's tick transmission going on.

Speaker 1 8:49

Okay.

PCR Testing And Lower-Cost Pooled Tests

Speaker 1 8:50

And how are cows tested for it?

Speaker 8:54

The Pennsylvania Animal Diagnostic Laboratory System, as well as other animal diagnostic laboratories, do offer a PCR test. Here in Pennsylvania, through the PADLS laboratory system, we do have what we call a duplex PCR. And so a single blood test can actually be tested for both thierelia orientalis and anaplasma. So anaplasma in cattle can show almost the exact same signs as thierelia orientalis.

Speaker 1 9:22

Okay.

Speaker 9:23

And so one of the recent changes we've made, in fact, this just occurred in January of this year, in addition to individual animal testing for animals that are potentially positive, animals that have signs of disease. We're also now offering here in the PADLS laboratory system pooled testing. And what that allows us to do, I mentioned earlier that if we know that there are positive animals and ticks, we can assume there's transmission. We can now pool up to 10 samples into a single test, which reduces the cost of tests per animal to identify if there's herd level prevalence of the disease. So now you can actually test 10 animals for the same price as testing one sick animal, which is a really economic way to understand if you have the disease circulating in your herd. You won't be able to identify individuals that have it, but it'll help you understand if it is there and how you can better manage your cattle as a herd moving forward.

Speaker 1 10:18

Okay. So that actually kind of leads into my next question.

Integrated Pasture And Tick Management

Speaker 1 10:21

How can we manage this and hopefully reduce our risk of this disease and tick exposure?

Speaker 10:28

So I think this is one of the more challenging ticks to manage just because of the really high populations it can cause. But it really comes down to the really time-tested strategy of integrated pest management. We want to look at multiple different ways that we can impact the tick and tick populations so that we can reduce the populations overall, reduce the risk of bites overall without increasing the risk of developing resistance to any of the medications we might be using to do this, or any of the chemicals we might be using to do this. Some of the things can be as simple and certainly things that anybody, whether they're organic or not, can do are things like clearing brush, minimizing shaded areas with taller vegetation, cutting tall grasses, and utilizing rotational grazing. These are all things that can help reduce the tick levels because these ticks really like warm, humid environments. And so those taller plants allow that for that more humid environment. If we can reduce that brush and some of those taller plants, we can help reduce the humidity and reduce tick populations.

Speaker 1 11:37

So are there certain times of the year when exposure to the Asian longhorn tick would be increased?

Speaker 11:44

There are. And so for the Northeast, and it varies in the south wher ewe have more consistent temperatures, but in the Northeast, we see the mymphs, so the second stage of these ticks, active in that June through August period. But I think the most significant time factor is that the larvae, the smallest of the ticks, have a really huge increase in activity in August and September, so that kind of late summer into fall period. These larvae, one of the more unique things about the Asian Longhorned tick is often we see the larvae of ticks preferring smaller species because they're smaller ticks, but we don't always see that with the Asian longhorned tick. These larvae are still very happy to bite our livestock species. So this big push of larvae in the late summer, early fall is probably one of our more significant periods for Asian longhorned tick risk, particularly in that swarming and exsanguination side of things.

Speaker 1 12:51

Okay.

Organic Limits Plus Herd Health Focus

Speaker 1 12:52

Is there anything that organic producers would be able to use as far as tools to control these ticks besides their pasture management?

Speaker 13:00

So our very limited products on the organic list that could be helpful. On operations where this tick has been identified, it would be important to discuss those options with your veterinarian and your organic certifier. But there really are pretty limited options. There are very few labeled products for the Asian longhorn tick in general for cattle. And of course, we have even fewer options in organic management. But the pasture management is going to be huge and it's going to be critical. And I think another thing we have to remember is particularly with the thierelia orientalis disease, one of the things that we see is we can see herds with very high disease problems. So we we see herds where we have a lot of animals being obviously sick. And we've also had herds where we know they're positive, but we really have seen no illness. And I think one of the things we have to remember is that the underlying health of the animal impacts their immune system. And that's going to impact their ability to fight disease. So I would really encourage, in terms of managing not just the tick, but also the thierelia orientalis, which nobody has a tool to manage. We do not have any labeled products to treat this disease. I think one of the best things for preventing problems associated with it is to maintain optimal health. So look at resources to make sure you're optimizing nutrition, make sure your cows are not suffering from other underlying diseases that might impact overall immune function. And so optimizing health, I think, is one of the most powerful tools we have to manage herds that are exposed to the Asian longhorn tick and thierelia orientalis genotype ikeda.

How Often To Test A Herd

Speaker 1 14:42

Okay, so keeping that in mind with producers trying to keep a closer eye on their herd health and testing for Thierelia orientalis, how often should they be testing for that?

Speaker 14:55

I think a lot of that is gonna depend on the herd. Once we know it's present, there may not be a lot of value in continuing to test. So if we suspect it in a specific animal, testing that animal can help us identify if it has the disease. And certainly if we're utilizing the Pennsylvania laboratory system, we have that duplex test. So it's going to rule out the top two diseases that cause this type of anemia in cattle. And so that can be a really valuable time to test. In terms of herds that are at risk, if you know that the tick is present, periodic testing would certainly be warranted. We haven't really come up with a real set time as to when to do that. But if you are negative, continuing to test maybe yearly, and certainly talk with your veterinarian about what that timeline should look like for the risk level for your herd. We can identify if it does enter the herd, which can help us manage how we move cattle and how we manage cattle within that herd. Once they're positive, the value of testing, I think, declines a fair bit.

Speaker 1 16:06

Okay. So this has been a lot of great information so far.

Practical Takeaways And PA Resources

Speaker 1 16:10

What would be your main takeaways that you would want dairy producers to know when it comes to the Asian longhorn tick and effectively managing it?

Speaker 16:19

I think the big things that are important is to understand if you have the tick, to understand if you have thierelia orientalis genotype ikeda, and to really focus on pasture management and maintaining optimal animal health. And I think in Pennsylvania, we have excellent resources for all of these. So certainly from testing for disease, we've got the Pennsylvania Animal Diagnostic Laboratory System. From this perspective of maintaining optimal health, pasture management, and even tick identification, Penn State Extension is an excellent resource. So we have a lot of resources that we can utilize here in Pennsylvania. And certainly our neighboring states have great extension systems as well that can help with this. And so I think just knowledge is really important. And then maintaining animal health is going to help you across the board. If we can optimize immune function, we're not just impacting thierelia, we're impacting every disease that could impact your cattle. And so I think those are really the keys to this. Know if you have the tick, know if you have the disease, and really optimize the health of your cattle.

Closing And Where To Get Help

Speaker 1 17:24

Great. Well, thank you to Dr. Springer for joining us today. It's been a lot of great information that you were able to share. If, as our listener, if you have any questions, feel free to reach out to your local dairy extension educator or your herd veterinarian to get more specific information for your herd. And don't forget to tune in to our next episode of Bovine Banter next Tuesday.